"Tires" is already a prefix choice in the Marketplace. That allows you to do a prefix search and see just tires that are for sale. Learn how to do this under Advanced Search.

Here's the catch:

The prefix doesn't get used much. Most common reasons:

People don't think to assign a prefix of "Tires" to their For Sale thread for tires, or don;t know that one exists

People don't know what that drop-down menu does that sits in front of their Thread Title on the Post New Thread page in the Marketplace forums. Instead of clicking on it and learning, they just ignore it.

The site owner will not add more meaningful prefixes, even though it is a good idea and has been brought up before. As a result, many people don't even bother using prefixes at all, or can't even if they wanted to since there is no prefix that applies to what they are trying to sell.

People can't read or prefer to do things the hard way. (This happens a lot around here.)